High temperature cooling process and system

ABSTRACT

A process and system for cooling a device subjected to high temperatures wherein a stream of coolant is flowed through the device. The resultant heated stream of coolant is passed in heat exchange relationship with a cooled stream of liquid heat transfer medium so that a quantity of heat is removed from the coolant substantially equal to the heat removed from the device. The stream of coolant is passed in heat exchange relationship with a heated stream of the liquid heat transfer medium so that the coolant is maintained at a desired temperature level and then the coolant is recirculated through the device.

[451 Sept. 3, 1974 HIGH TEMPERATURE COOLING PROCESS AND SYSTEM [75]Inventors: Robert E. McMinn; Mickey B.

' Jamison, both of Oklahoma City,

Okla.

[73] Assignee: Black, Sivalls & Bryson, Inc.,

Oklahoma City, Okla.

22 Filed: Jan. 15, 1973 211 Appl. No.2 323,996

[52] US. Cl 165/107, 165/30, 239/132, 239/132.3, 266/34 L [51] Int. Cl.F28d 15/00 [58] Field of Search 165/107; 239/132, 132.1, 239/1323,132.5; 266/34 L, 34 LM [56] References Cited UNITED STATES PATENTS1,905,811 4/1933 Culver 165/107 2,832,733 4/1958 Szilard 176/523,008,271 11/1961 Cook 165/107 3,059,913 10/1962 Sands 165/107 3,537,51511/1970 Byrd 165/107 H54 TEE SL/EGE MD STORAGE VESSEL FOREIGN PATENTS ORAPPLICATIONS 187,553 12/1905 Germany 165/107 545,299 10/1922 France165/107 962,498 7/1964 Great Britain 165/107 Primary ExamineF-Manu'el A.Antonakas Assistant Examiner-Daniel J. OConnor Attorney, Agent, orFirm-C. Clark Dougherty, Jr.

[5 7 ABSTRACT A process and system for cooling a device subjected tohigh temperatures wherein a stream of coolant is flowed through thedevice. The resultant heated stream of coolant is passed in heatexchange relationship with a cooled stream of liquid heat transfermedium so that a quantity of heat is removed from the coolantsubstantially equal to the heat removed from the device. The stream ofcoolant is passed in heat exchange relationship with a heated stream ofthe liquid heat transfer medium so that the coolant is maintained at adesired temperature level and then the coolant is recirculated throughthe device.

13 Claims, 1 Drawing Figure SURGE 4N0 EXPA/VS/OA/ VE55EL OXYGE'A/ LANCEPATENIEDISEP 31914 Saws Nubia \xuNOXXQ HIGH TEMPERATURE COOLING PROCESSAND SYSTEM BACKGROUND OF THE INVENTTON 1. Field of the Invention A Thepresent invention relates to a process and system for cooling a devicesubjected to high temperatures, and more particularly, but not by way oflimitation, to a process and system for cooling a device for introducingmaterials into the interior of a highly heated chamber.

2. Description of the Prior Art In many industrial processes, such as inthe refining of metals, it is necessary to introduce materials intohighly heated chambers by means of material introduction devices. Forexample, in the steel industry, introduction devices known as lances arecommonly used for introducing oxygen or oxygen enriched air into moltenmetal so that impurities in the metal are removed. Commonly, the lancenozzle is positioned beneath the surface of the molten metal therebysubjecting the lance to extremely high temperatures, e.g., 2,000F to3,000F. To withstand these temperatures such introduction devices mustbe continuously cooled. Heretofore, the cooling has been accomplished bycirculating a cooling medium, generally at high pressures, through heatexchange passages disposed in the device. While these prior coolingsystems have been used successfully, often they have not removed heatfrom the device being cooled at a uniform rate, causing prematurefailure of the device. Also, the use of a liquid cooling medium such aswater to cool such devices at relatively high pressures is dangerous inthat upon failure of the device, leakage of the liquid cooling mediuminto the high temperature zone can result in explosions, etc.

By the present invention an improved process and system for cooling adevice subjected to high temperatures is provided which includescirculating a coolant through the device at low pressures.

SUMMARY OF THE INVENTION The present invention relates to a process forcooling a device subjected to high temperatures which comprises thesteps of flowing a stream of coolant through the device so that heat istransferred into the stream of coolant and the device is cooled, passingthe resultant heated stream of coolant in heat exchange relationshipwith a cooled stream of a liquid heat transfer medium so that a quantityof heat is removed from the stream of coolant substantially equal to theheat removed from the device. passing the stream of coolant in heat exchange relationship with a heated stream of the liquid heat transfermedium so that the stream of coolant is maintained at a desiredtemperature level and recirculating the stream of coolant through thedevice. Systems for carrying out the process of the invention are alsoprovided.

It is, therefore, a general object of the present invention to providean improved process and system for cooling a device subjected to hightemperatures.

A further object of the present invention is the provision of a processfor cooling a device subjected to high temperatures wherein a stream ofcoolant is circulated through the device at low pressures so that heatis removed from the device at a uniform rate and the possibility ofexplosion is minimized.

Yet a further object of the present invention is the provision of aprocess for cooling a device subjected to high temperatures with astream of coolant wherein a single liquid heat transfer medium'isutilized to achieve both heating and cooling of the stream of coolant.

Still another object of the present invention is the provision of asystem for cooling a device subjected to high temperatures which isrelatively simple and inexpensive to install and operate. I

Other and further objects and advantages of the present invention willbe readily apparent to those skilled in the art upon a reading of thedescription of preferred embodiments of the invention taken inconjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the DRAWING, a system of the presentinvention is illustrated in diagrammatic form.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the'drawing, asystem of the present invention is illustrated diagrammatically,generallydesignated by the numeral 10. The system 10 is shown connectedto a device 12 which may be any of a variety of devices which aresubjected to high temperatures and which include heat exchange passagesdisposed therein for circulating a cooling medium therethrough. In thedrawing, the device 12 is illustrated in the form of an oxygen lance,and includes an inner tubular member 16 having a pair of cylindricalouter enclosure members 18 and 20 concentrically attached thereto. Thetubular member 16 includes a nozzle at its lower end 17 for emittingoxygen into a highly heated chamher. The enclosure members 18 and 20form'annular passages for the flow of a stream of coolant which removesheat from the lance components and prevents the lance from becomingoverheated.

The stream of coolant enters the lance 12 by way of a connection 22disposed in the enclosure member 20 and flows through the annular spaceformed between the walls of the enclosure members 18 and 20 to the otherend 17 of the lance 12. The stream of coolant then enters the annularspace formed between the walls of the enclosure member 18 and thetubular member 11 and flows to the other end of the lance 12 from whereit exits by way of a connection 24 attached to the enclosure member 18.

The system 10 for circulating the stream of coolant through the device12 so that the device 12 is continuously cooled includes a vessel 26 forcharging the system 10 with coolant. The charge vessel 26 may take avariety of forms, but preferably includes an insulated outer enclosure28 having inlet and outlet connections 30 and 32 therein, and an innershell 34 disposed within the outer enclosure 28. The inner shell 34 ispositioned within the enclosure 28 in .a manner such that a passageway35 is formed between the outer enclosure 28 and the inner shell 34 whichis communicated with the inlet and outlet connections 30 and 32. As willbe described further hereinbelow, a heated liquid heat transfer mediumis circulated through the passageway 35 of the vessel 26 and the innershell 34 thereof forms a container for receiving a charge of coolant andmaintaining it in the molten state. The charge vessel 26 furtherincludes a coolant inlet connection 36 and a coolant outlet connection38 which are attached to the inner shell 34 in a manner such that astream of coolant can be flowed by way of the connections 36 and 38 toand from the inner shell 34 without communicating with the liquid heattransfer medium flow passage 35. The coolant outlet connection 38 isconnected to a conduit 40 which is in turn connected to the inlet of aconventional pump 42 which has the capability of pumping the stream ofcoolant utilized. The conduit 40 includes an outer cylindrical shell 44concentrically attached thereto in a manner such that an annular flowpassage is formed between the conduit 40 and the shell 44. The dischargeconnection of the pump 42 is connected to a conduit 46 having acylindrical shell 48 concentrically attached thereto so that an annularflow passage is formed between the conduit 46 and shell 48.; The conduit46 is connected to the inlet connection 22 of the lance 12. The coolantoutlet connection 24 of the lance 12 is connected to a conduit 50 whichincludes a cylindrical shell 52 concentrically attached thereto. Theconduit 50 is connected to a conventional heat exchanger 54. Preferably,the heat exchanger 54 is of the shell and tube type with the conduit 50connected to the tube side inlet connection thereof. The tube sideoutlet connection of the exchanger 54 is connected to a conduit 56 whichis in turn connected to the coolant inlet connection 36 of the chargevessel 26 previously described. The conduit 56 includes an outercylindrical shell 58 concentrically attached thereto forming a flowpassage between the conduit 56 and the outer shell 58.

As will be understood, the various flow passages formed by thecylindrical shells 44, 48, 52 and 58 and conduits 40, 46, 50 and 56respectively are connected together in series so that a stream of heatedliquid heat transfer medium can be flowed through the flow passages andthe various conduits are heated. That is, one end of the cylindricalshell 44 is connected to a conduit 60 which conducts the stream ofheated liquid heat transfer medium thereto. The other end of the shell44 is connected to the shell 48 by a conduit 62. The shell 48 isconnected to the shell 52 by a conduit 64 and the shell 52 is connectedto the shell 58 by a conduit 66. A conduit 68 is connected to the shell58 for withdrawing the stream of heated liquid heat transfer medium aswill be described further hereinbelow.

The system 10 includes a liquid heat transfer medium heating circuitcomprised of a conventional heater 70 having a heating coil 72 disposedtherein. The outlet connection 73 of the heating coil 72 is connected bya conduit 74 to the liquid heat transfer medium inlet connection 30 ofthe charge vessel 26. The liquid heat transfer medium outlet connection32 of the charge vessel 26 is connected by a conduit 76 to a surge andexpansion tank 77. The conduit 68 previously described connected to thecylindrical shell 58 is connected to the conduit 76, and a conduit 78 isalso connected to the conduit 76. The other end of the conduit 78 isconnected to the inlet of a conventional pump 80. The discharge of thepump 80 is connected to a conduit 82 which is in turn connected to theinlet connection 84 of the heating coil 72.

A liquid heat transfer medium cooling circuit is provided in the system10 which includes a surge tank 86 having inlet and outlet connections 88and 90 disposed therein. The outlet connection 90 of the surge tank 86is connected by a conduit 92 to the inlet connection of a conventionalpump 94. The discharge connection of the pump 94 is connected by aconduit 96 to the shell side inlet connection of the heat exchanger 54.The shell side outlet connection of the exchanger 54 is connected by aconduit 98 to a conventional cooler 100. The cooler 100 may take any ofa variety of forms, but is preferably a conventional forced atmosphericair heat exchanger. A conduit 102 connects the outlet connection of thecooler 100 to the inlet connection 88 of the surge tank 86.

A conduit 104 is connected between the conduit 96 and the conduit 82,and a shutoff valve 106 is disposed in the conduit 104. As will beunderstood by those skilled in the art, the system 10 includesconventional valves, instruments and controls (not shown) forcontrolling the flow rates, temperatures, and other conditions of thestreams of coolant and liquid heat transfer medium flowing therethrough.

OPERATION OF THE SYSTEM 10 In operation of the system 10, a charge ofthe coolant material utilized to cool the device 12 is introduced intothe charge vessel 26, i.e., into the inner shell 34 of the charge vessel26. The coolant used can be any of a variety of metals, mixtures ofmetals or other materials having a melting point below about 600F.Preferably, the coolant is a metal or a mixture of metals which will notcause an explosion or other hazardous condition if it leaks into ahighly heated chamber upon failure of the device 12. The most preferredcoolant for use in accordance with the present invention is a eutecticmixture of lead and bizmuth having a melting point of about 270F.

A stream of heated liquid heat transfer medium is continuouslycirculated through the passage 35 of charge vessel 26 and through theheating circuit of the system 10. While a variety of liquid heattransfer materials may be used, a commercial high temperature heattransfer oil having a flash point above about 600F is preferred.

The liquid heat transfer medium is pumped by the pump 80 through theconduit 82 and through the heating coil 72 of the heater 70. Whilepassing through the heating coil 72, the stream of liquid heat transfermedium is heated to a temperature of approximately 600F. The thus heatedliquid heat transfer medium exits the flow coil 72 of the heater 70 andpasses I through the conduit 74. A major portion of the stream of heatedliquid heat transfer medium flows through the passageway 35 of thecharge vessel 26 thereby heating the charge vessel 26 and the charge ofcoolant material contained therein. A minor portion of the heated liquidheat transfer medium flows from the conduit 74 into the conduit 60 andthrough the flow passages formed by the shells 44, 48, 52 and 58attached to the conduits 40, 46, 50 and 56, and through the conduits 62,64 and 66 connecting the shells together in series. As will beunderstood, the conduits 40, 46, 50 and 56 are heated by the flow ofheated liquid heat transfer medium through the passages formed by thecylindrical shells 44, 46, 52 and 58.

The portion of the liquid heat transfer medium flowing through thepassageway 35 of charge vessel 26 exits the vessel 26 by way of theconnection 32 and the conduit 76 and flows into the conduit 78. Theportion of the liquid heat transfer medium flowing through thecylindrical shells 44, 48, 52 and 58 passes by way of the conduit 68into the conduit 76 where it combines with the portion from the vessel26. The vessel 77 is connected to the conduit 76 and functions as asurge and thermal expansion chamber. The combined stream of liquid heattransfer medium passes from the conduit 76 through the conduit 78 intothe suction of the pump 80. Thus, as will be understood, a stream ofliquid heat transfer medium is continuously circulated through theheating circuit of the system 10, i.e., through the heater 70, thecharge vessel 26, and the flow passages formed by the shells 44, 48, 52and 58 so that the coolant charged to the charge vessel 26 is melted andmaintained at a desired temperature level, e.g., in the molten state, asit is circulated through the device 12.

A stream of coolant is pumped by the pump 42 to the device 12 by way ofthe conduit 46. The stream of coolant flows through the device 12 sothat heat is removed therefrom and the resultant heated stream ofcoolant exits the device 12 by way of the conduit 50. From the conduit50 the stream of coolant passes through the tube side of the heatexchanger 54 wherein a quantity of heat substantially equal to the heatremoved from the device 12 is removed from the stream of coolant. Fromthe heat exchanger 54 the stream of coolant passes by way of the conduit56 through the inlet connection 36 of the charge vessel 26 and into theinner shell 34 thereof. From the charge vessel 26 the stream of coolantpasses by way of the conduit 44 to the suction connection of the pump42. The stream of coolant is continuously circulated through the device12 and the system so that the device 12 is continuously cooled.

The stream of heated liquid heat transfer medium passing through thecharge vessel 26 and the flow passages formed between the shells 44, 48,52 and 58 functions to maintain the stream of coolant at a desiredminimum temperature as it is circulated. For example. when the coolantused is a metal or mixture of metals, the temperature thereof ismaintained at a level so that the coolantremains in the molten state.Further. in the event the system 10 is shut down and the coolant allowedto solidify within the system 10, the solidified coolant can be quicklyremelted by circulating the heated liquid heat transfer medium throughthe system 10 prior to starting circulation of the stream of coolantthrough the device 12.

A stream of the liquid heat exchange medium is continuously circulatedthrough the shell side of the heat exchanger 54 and through the coolingcircuit of the system 10 to continuously remove a quantity of heat fromthe stream of coolant substantially equal to the heat removed from thedevice 12. That is. a stream of liquid heat transfer medium is pumped bythe pump 94 through the conduit 96 and into the shell side of the heatexchanger 54. As the stream of liquid heat transfer medium flows throughthe heat exchanger 54 it passes in heat exchange relationship with thestream of coolant so that heat is transferred from the coolant to theheat transfer medium. The thus heated liquid heat transfer medium flowsfrom the heat exchanger 54 by way of the conduit 98 to the cooler 100.As will be anderstood. the quantity of heat removed from the stream ofliquid heat transfer medium by the coolor 100 is controlled at a levelequal to the quantity of heat added to the stream of liquid heattransfer medium as it passes through the heat exchanger 54. From thecooler 100 the stream of liquid heat transfer medium flows by way of theconduit 102 into the surge vessel 86. From the surge vessel 86, thestream of liquid heat transfer medium flows by way of the conduit 92 tothe suction of the pump 94.

As the system 10 is operated to continuously cool the device 12additional coolant required is added to the system 10 by way of thecharge vessel 26. Prior to starting up the system 10 a quantity ofliquid heat transfer medium is added to the surge vessel 86 through afillv connection thereof (not shown). The pump 94 is then started sothat a stream of the heat transfer medium is caused to flow through thecooling circuit of the system 10. The valve 106 disposed in the conduit104 is next opened so that a quantity of the liquid heat transfer mediumis caused to flow into the heating circuit of the system 10 and into thesurge and expansion vessel 77 thereof. Once the system 10 is chargedwith liquid heat transfer medium in this manner, the pump is started tocause a stream of the liquid heat transfer medium to circulate throughthe heating circuit of the system 10. As the system 10 is operatedadditional liquid heat transfer medium required is added to the surgevessel 86.

The various streams of coolant and liquid heat transfer medium arecirculated through the system 10 at low 7 pressure levels therebyallowing the use of low pressure equipment and obviating hazardsassociated with the operation of high pressure systems. Additionally, bythe process and system of the present invention, a single liquid heattransfer medium is utilized for both cooling the stream of coolant usedto cool the device 12 and maintaining the stream of coolant in themolten state.-

As mentioned above, the use of a stream of coolant such as a stream ofmolten metal is advantageous in that if the device 12 fails and thecoolant enters a highly heated chamber into which the device 12 isinserted, the possibility of an explosion is minimized.

Thus, the present invention is well suited to carry out the objects andadvantages mentioned as well those inherent therein. While presentlypreferred embodiments of the invention are given for the purpose of thisdisclosure, numerous changes in the details of the process and systemand arrangement of steps and parts can be made which will readilysuggest themselves to those skilled in the art andwhich are encompassedwithin the spirit of the invention and the scope of the appended claims.

What is claimed is:

i l. A process for cooling a-lance subjected to high temperatures whichcomprises the steps of:

a. flowing a stream of coolant having a melting point in the range offrom about 270F to about 600F through said lance so that heat istransferred into the stream of coolant and the lance is cooled;

b. passing the resultant heated stream of coolant in heat exchangerelationship with a cooled stream of a liquid heat transfer medium sothat a quantity of 1 2. The process of claim 1 wherein the coolant is aeutectic mixture of lead and bizmuth.

3. The process of claim 2 wherein the liquid heat transfer medium ishigh temperature heat transfer oil having a flash point above about600F.

4. A process for continuously cooling a lance for introducing materialsinto the interior of a highly heated chamber which comprises the stepsof:

a. flowing a stream of molten metal through said device so that heat istransferred into the stream of molten metal and the device is cooled;

b. passing the resultant heated stream of molten metal in heat exchangerelationship with a first stream of liquid heat transfer medium so thata quantity of heat is continuously removed from said stream of moltenmetal substantially equal to the quantity of heat transferred thereintofrom said lance;

c. passing the stream of molten metal in heat transfer relationship witha second stream of liquid heat transfer medium so that the stream ofmolten metal is maintained in the molten state; and

d. continuously recirculating said stream of molten metal through saidlance.

5. The process of claim 4 wherein the molten metal has a melting pointbelow about 600F.

6. The process of claim 5 wherein the molten metal is a eutectic mixtureof lead and bizmuth.

7. The process of claim 6 wherein the liquid heat transfer medium ishigh temperature heat transfer oil having a flash point above about600F.

8. The process of claim 7 wherein the first stream of liquid heattransfer medium is continuously circulated in a cooling circuit whereinit is cooled to a temperature of about 1 l5F.

9. The process of claim 8 wherein the second stream of liquid heattransfer medium is continuously circulated in a heating circuit whereinit is heated to a temperature of about 600F.

10. A system for cooling a lance subjected to extra high temperatures,said system including a lance having heat exchange passages forcirculating a stream of coolant therethrough to remove heat therefromand which comprises:

a heated charge vessel for receiving and melting a charge of coolant,said charge vessel having coolant inlet and outlet connections disposedtherein;

first conduit means connected between the heat exchange passages of saidlance and the coolant inlet and outlet connections of said chargevessel;

first heat exchange means connected in said first conduit means forcooling the stream of coolant whereby a quantity of heat is removedtherefrom substantially equal to the quantity of heat removed from saidlance;

second heat exchange means connected to said charge vessel and to saidfirst conduit means for heating said charge vessel and said firstconduit means whereby the stream of coolant is maintained at a desiredtemperature level; and

pump means disposed in said first conduit means for circulating thestream of coolant through said conduit means, through the heat exchangepassages of said lance, through the first and second heat exchange meansand through the heated charge vessel.

11. The system of claim 10 wherein the first heat exchange meanscomprises:

a heat exchanger for passing the stream of coolant in heat exchangerelationship with a cooled stream of liquid heat transfer medium;

means for cooling the stream of liquid heat transfer medium;

second conduit means connected between said heat exchanger and saidmeans for cooling the stream of liquid heat transfer medium; and

pump means disposed in the second conduit means for continuouslycirculating the stream of liquid heat transfer medium through saidsecond conduit means, said heat exchanger and said means for cooling thestream of liquid heat transfer medium.

12. The system of claim 11 wherein the means for cooling the stream ofliquid heat transfer medium is an atmospheric air heat exchanger.

13. The system of claim 10 wherein the second heat exchange meanscomprises:

said charge vessel including heat exchange passages disposed therein forcirculating heated liquid heat transfer medium therethrough whereby saidcharge vessel is heated;

said first conduit means including heat exchange passages forcirculating heated liquid heat transfer medium therethrough whereby theconduit means are heated;

a liquid heat transfer medium heater;

third conduit means connected between the heat exchange passages of thecharge vessel, the heat exchange passages of the first conduit means andthe liquid heat transfer medium heater; and

pump means disposed in said third conduit means for circulating a streamof liquid heat transfer medium through the third conduit means, saidheater and the heat exchange passages of the charge vessel and the firstconduit means.

1. A process for cooling a lance subjected to high temperatures whichcomprises the steps of: a. flowing a stream of coolant having a meltingpoint in the range of from about 270*F to about 600*F through said lanceso that heat is transferred into the stream of coolant and the lance iscooled; b. passing the resultant heated stream of coolant in heatexchange relationship with a cooled stream of a liquid heat transfermedium so that a quantity of heat is removed from said stream of coolantsubstantially equal to the heat transferred thereinto from said lance;c. passing the stream of coolant in heat exchange relationship with aheated stream of the liquid heat transfer medium so that the stream ofcoolant is maintained at a desired temperature level; and d.recirculating the stream of coolant through said lance.
 2. The processof claim 1 wherein the coolant is a eutectic mixture of lead andbizmuth.
 3. The process of claim 2 wherein the liquid heat transfermedium is high temperature heat transfer oil having a flash point aboveabout 600*F.
 4. A process for continuously cooling a lance forintroducing materials into the interior of a highly heated chamber whichcomprises the steps of: a. flowing a stream of molten metal through saiddevice so that heat is transferred into the stream of molten metal andthe device is cooled; b. passing the resultant heated stream of moltenmetal in heat exchange relationship with a first stream of liquid heattransfer medium so that a quantity of heat is continuously removed fromsaid stream of molten metal substantially equal to the quantity of heattransferred thereinto from said lance; c. passing the stream of moltenmetal in heat transfer relationship with a second stream of liquid heattransfer medium so that the stream of molten metal is maintained in themolten state; and d. continuously recirculating said stream of moltenmetal through said lance.
 5. The process of claim 4 wherein the moltenmetal has a melting point below about 600*F.
 6. The process of claim 5wherein the molten metal is a eutectic mixture of lead and bizmuth. 7.The process of claim 6 wherein the liquid heat transfer medium is hightemperature heat transfer oil having a flash point above about 600*F. 8.The process of claim 7 wherein the first stream of liquid heat transfermedium is continuously circulated in a cooling circuit wherein it iscooled to a temperature of about 115*F.
 9. The process of claim 8wherein the second stream of liquid heat transfer medium is continuouslycirculated in a heating circuit wherein it is heated to a temperature ofabout 600*F.
 10. A system for cooling a lance subjected to extra hightemperatures, said system including a lance having heat exchangepassages for circulating a stream of coolant therethrough to remove heattherefrom and which comprises: a heated charge vessel for receiving andmelting a charge of coolant, said charge vessel having coolant inlet andoutlet connections disposed therein; first conduit means connectedbetween the heat exchange passages of said lance and the coolant inletand outlet connections of said charge vessel; first heat exchange meansconnected in said first conduit means for cooling the stream of coolantwhereby a quantity of heat is removed therefrom substantially equal tothe quantity of heat removed from said lance; second heat exchange meansconnected to said charge vessel and to said first conduit means forheating said charge vessel and said first conduit means whereby thestream of coolant is maintained at a desired temperature level; and pumpmeans disposed in said first conduit means for circulating the stream ofcoolant through said conduit means, through the heat exchange passagesof said lance, through the first and second heat exchange means andthrough the heated charge vessel.
 11. The system of claim 10 wherein thefirst heat exchange means comprises: a heat exchanger for passing thestream of coolant in heat exchange relationship with a cooled stream ofliquid heat transfer medium; means for cooling the stream of liquid heattransfer medium; second conduit means connected between said heatexchanger and said means for cooling the stream of liquid heat transfermedium; and pump means disposed in the second conduit means forcontinuously circulating the stream of liquid heat transfer mediumthrough said second conduit means, said heat exchanger and said meansfor cooling the stream of liquid heat transfer medium.
 12. The system ofclaim 11 wherein the means for cooling the stream of liquid heattransfer medium is an atmospheric air heat exchanger.
 13. The system ofclaim 10 wherein the second heat exchange means comprises: said chargevessel including heat exchange passages disposed therein for circulatingheated liquid heat transfer medium therethrough whereby said chargevessel is heated; said first conduit means including heat exchangepassages for circulating heated liquid heat transfer medium therethroughwhereby the conduit means are heated; a liquid heat transfer mediumheater; third conduit means connected between the heat exchange passagesof the charge vessel, the heat exchange passages of the first conduitmeans and the liquid heat transfer medium heater; and pump meansdisposed in said third conduit means for circulating a stream of liquidheat transfer medium through the third conduit means, said heater andthe heat exchange passages of the charge vessel and the first conduitmeans.